Bram Moolenaar wrote:
> Karsten Hopp wrote:
>
>> We've rebuilt all Fedora-12 packages and vim was one of the programs
>> that failed to
>> run with enhanced glibc fortify features:
>>
>> vi
>> *** buffer overflow detected ***: vim terminated
>> ======= Backtrace: =========
>> /lib64/libc.so.6(__fortify_fail+0x37)[0x7f780f90df47]
>> /lib64/libc.so.6[0x7f780f90bee0]
>> vim(eval_init+0x6f)[0x45a5cf]
>> vim(main+0x82)[0x4ac952]
>> /lib64/libc.so.6(__libc_start_main+0xfd)[0x7f780f835aed]
>> vim[0x422069]
>>
>>
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=514717 has all the details
>> and 2 suggested fixes.
>
> What Vim does is completely fine. So your library is broken. I
> understand that it's intentionally broken to find buffer overflows.
>
> Now, we could work around the broken library. The diff shows one
> solution. But this would actually be needed in many more places, it
> just fixes the one found on startup. When running Vim there are more.
> Takes a long time to find them all.
>
> A proper fix would be:
> - Add configure check for the broken library.
> - When the library is broken use another function instead of STRCPY() to
> avoid using the broken strcpy(). It's slower but should work.
>
> A better solution would be to tell the library not to have this check
> for what it guessed the destination size would be. Is there an option
> or #define for this?
There is such a compilation option: -D_FORTIFY_SOURCE=0
Patch 7.2.044 already fixed crash which happened because of
the Fortify feature. It was fixed by compiling Vim with
-D_FORTIFY_SOURCE=1. Some versions of gcc compile
by default with -D_FORTIFY_SOURCE=2 (that's the case for
Ubuntu at least). -D_FORTIFY_SOURCE=2 can in some cases
cause valid programs to crash, which is the case for Vim.
As far as I understand, -D_FORTIFY_SOURCE=1 still has
some checks but they are relaxed a bit from -D_FORTIFY_SOURCE=2.
Compiling with -D_FORTIFY_SOURCE=1 should not break
Vim. I never see any problem with Vim using -D_FORTIFY_SOURCE=1.
But if you want to completely disable the Fortify feature, you can compile
with -D_FORTIFY_SOURCE=0 (or -U_FORTIFY_SOURCE)
This is the Patch in which introduces -D_FORTIFY_SOURCE=1:
===============
Patch 7.2.044
Problem: Crash because of STRCPY() being over protective of the destination
size. (Dominique Pelle)
Solution: Add -D_FORTIFY_SOURCE=1 to CFLAGS. Use an intermediate variable
for the pointer to avoid a warning.
Files: src/auto/configure, src/configure.in, src/eval.c
===============
Is Fedora compiling Vim with -D_FORTIFY_SOURCE=1 or
-D_FORTIFY_SOURCE=2?
In the absense of -D_FORTIFY_SOURCE compilation option,
gcc might using -D_FORTIFY_SOURCE=2 by default (as it is the
case on Ubuntu) which is known to break vim and was fixed
in patch 7.2.044.
The configure script checks whether to add -D_FORTIFY_SOURCE=1
to the compilation options. Perhaps this is not happing on Fedora?
Can you give the compilation log to see what compilation options
were used?
-- Dominique
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